Power cloud developing apparatus with a first and second electric field curtain generating means

Abstract

A developing apparatus for use in an electrophotographic apparatus and like, which is adapted to supply a developing material without contact between a developing material support member and an image holding member by utilizing the action of an electric field curtain, wherein the developing material can be transported to the image holding member with requiring no necessities for a large voltage to be impressed thereto and for floating, so that it is prevented that the developing material is scattered during the transportation thereof or a formed image is subjected to fogging.

What is claimed is: 
     
       1. A developing apparatus which comprises: an electrostatic latent image bearing member for bearing an electrostatic latent image;   a developer transporting member for transporting a developer along its surface;   a first electric field curtain generating means for generating a powder cloud of the developer on the surface of said developer transporting member by electric field curtain force, for causing an electric field curtain to act at positions except for a developing area where said developer transporting member confronts with said electrostatic latent image bearing member; and   a second electric field curtain generating means disposed between said electrostatic latent image bearing and said developer transporting member so as to supply the developer of the powder cloud to the electrostatic latent image at the developing area by electric field curtain force.   
     
     
       2. A developing apparatus which comprises: developer transporting means for transporting a layer of developer along its surface and including a plurality of first electrodes to which an alternating current voltage is applied;   an electrostatic latent image bearing member for bearing an electrostatic latent image, said electrostatic latent image bearing member disposed to confront with said developer transporting means so as to define a developing region therebetween;   a plurality of second electrodes disposed at said developing region and being applied thereto an alternating current voltage;   first applying means for applying the alternating current voltage to said first electrodes except in the area corresponding to said developing region so as to form a powder cloud of the developer where the alternating current voltage is applied; and   second applying means for applying the alternating current voltage to said second electrodes so as to attract the powder cloud of the developer to the developing region to develop the electrostatic latent image.   
     
     
       3. A developing apparatus as claimed in claim 2, wherein said developer transporting means is a rotatably disposed cylindrical shaped member. 
     
     
       4. A developing apparatus as claimed in claim 2, wherein said first alternating voltage applying means including bias voltage applying means for applying a bias voltage to the developer transporting means in the area corresponding to said developing region. 
     
     
       5. A developing apparatus as claimed in claim 2, which further comprises: a developer supply means for supply developer onto said developer transporting means, said developer supply means including charging means for charging the developer before the developer is supplied said developer transporting means.   
     
     
       6. A developing apparatus as claimed in claim 5, wherein said charging means comprises a rotating roller and a pressing member pressing the surface of the roller wherein developer is pressed by said pressing member so as to be frictionally charged. 
     
     
       7. A developing apparatus which comprises: a developer support member for supporting a developer on its surface;   an electrostatic latent image bearing member for bearing an electrostatic latent image, said electrostatic latent image bearing member disposed to confront with said developer support member so as to define a developing region therebetween;   driving means for rotating said developer support member;   a first group of electrodes provided on the surface of developer support member and insulated from each other;   a first alternating voltage applying means for applying alternating current voltage to said first group of electrodes in an area except where said developer support member confronts with said electrostatic latent image bearing member so as to transport developer with forming a powder cloud of the developer by electric field curtain force when said developer support member is rotated by the driving means;   a second group of electrodes provided at the developing region and provided along a direction parallel to the rotating axis of said developer support member; and   a second alternating voltage applying means for applying alternating current voltage between neighboring electrodes of said second group of electrodes so as to supplying the transported developer to the electrostatic latent image by electric field curtain force.   
     
     
       8. A developing apparatus for developing an electrostatic latent image, which comprises; an electrostatic latent image bearing member for bearing an electrostatic latent image;   a developer support member provided to confront said electrostatic latent image bearing member;   driving means for rotating said developing support member;   a first group of electrodes provided on the surface of said developer support member and insulated from each other;   an inner roller built in said support member;   a second group of electrodes each provided corresponding to said first group of electrodes in a side end face of said support member to be electrically connected with said first group of electrodes;   a third group of electrodes each provided in a side end face of said inner roller in an area except where said developer support member confronts said electrostatic latent image bearing member, said third group of electrodes are periodically touched with said second group of electrodes in accordance with the rotation of the developer support member by the driving means;   a first alternating voltage source for applying an alternating current voltage to said third group of electrodes, wherein the alternating current voltage is applied to said second group of electrodes through said third group of electrodes so as to generate an electric field curtain so that the developer forms a powder cloud on the surface of the developer support member by electric field curtain force when said developer support member is rotated by the driving means;   a fourth group of electrodes provided between said electrostatic latent image bearing member and said developing material support member and provided along a direction parallel to the rotating axis of said developer support member; and   a second alternating voltage applying means for applying alternating current voltage between neighboring electrodes of said fourth group of electrodes so as to supplying the generated powder cloud to the electrostatic latent image by electric field curtain force.